WO2010023060 discloses a curable composition and a process for forming a polyisocyanurate by combining an isocyanate-reactive mixture comprising a polyol, an anhydride and a trimerization catalyst with a polyisocyanate. The trimerization catalyst is selected from alkali metal carboxylates, quaternary ammonium carboxylates and mixtures thereof, the carboxylate having 1-12 carbon atoms.
In U.S. Pat. No. 3,970,600 stable solutions of isocyanurate-polyisocyanates containing amide and/or acylurea groups have been described. They avoid deposition of fine or coarse crystalline solids in polyisocyanates comprising isocyanurate groups. First a polyisocyanate is reacted with polybasic carboxylic acid to prepare a polyisocyanate with amide and/or—substituted—acylurea groups. Then this polyisocyanate is trimerized to form an isocyanurate-polyisocyanate and this conversion is stopped by adding acid.
In JP 2-110123 an aliphatic diisocyanate is trimerized to prepare polyisocyanates which have an isocyanurate structure using a catalyst and a deactivating agent once the desired degree of conversion has been attained (in other words the deactivating agent is used as terminating agent to stop the trimerization reaction). The deactivating agent has the structure —CO—NH2 or —SO—NH2 and may be urea, methyl urea, 1,1-dimethyl urea, phenyl carbamate, ethylcarbamate or butylcarbamate. Subsequently deactivated catalyst, excess diisocyanate and solvent, if used, are eliminated. By using this deactivating agent the polyisocyanate comprising polyisocyanurate structure shows a lower degree of discoloration. JP 2-110123 does not disclose further curable polyisocyanurate comprising materials.
EP0435060 discloses a liquid casting composition prepared by reacting polyisocyanates with an organic compound containing at least two epoxide groups in a quantity corresponding to an equivalent ratio of isocyanate groups to epoxide groups of about 1.2:1 to about 500:1 and a tertiary amine as catalyst until an intermediate product having a conversion of max. 65% of the isocyanate groups is achieved by adding a stabilizing component comprising at least one alkylating sulfonic acid alkyl ester. Because the reaction does not stop automatically, a stabilizing agent must be added once a conversion of max. 65% of the isocyanate groups is achieved in order to stop the reaction which makes the process very difficult to stear in advance. Further reaction may be obtained by adding subsequently a heat-activatable catalyst selected from tertiary and/or quaternary ammonium salts of an alkylating or acidic ester of organic phosphonic acid and/or addition of complex of boron trihalides with tertiary amines.
US2004/0176562 discloses a method for the production of stable, low-odor, monomer-containing polyisocyanurates of isophorone di-isocyanate (IPDI). The process involves trimerization in presence of quat. hydroxyalkylammonium compounds followed by a thermal deactivation of the catalyst at 100-160° C.
WO 2008/068198 and US 2010/0022707 disclose a process for preparing an oligomerized polyisocyanate using a catalyst wherein a deactivator is used once the desired conversion has been obtained followed by removal of the polyisocyanate which was not converted. The deactivator may be selected from urea and urea containing compounds, amongst others.
EP 585835 discloses a process for preparing isocyanurate and urethane group containing polyisocyanate mixtures by partially cyclizing diisocyanates in the presence of a trimerization catalyst, deactivating the trimerization catalyst when the desired conversion is achieved, and subsequently reacting the resulting isocyanurate group containing polyisocyanate with hydroxyl compounds and then separating off the monomeric diisocyanate.
Further disclosures related to partially trimerized polyisocyanate compositions using different methods to stop the trimerization are: EP 447093, U.S. Pat. No. 4,284,730, U.S. Pat. No. 4,537,961, U.S. Pat. No. 4,697,014, U.S. Pat. No. 4,743,627, U.S. Pat. No. 5,124,370, U.S. Pat. No. 5,221,743 and U.S. Pat. No. 7,553,963. None of these disclosures reveal the present invention or point into its direction.
In U.S. Pat. No. 7,071,353 reaction products of isocyanates and carboxylic acids are disclosed. First amides are formed which then form acylureas by reaction with further isocyanate groups.
Thermally activated PIR catalysis has been disclosed in U.S. Pat. No. 6,127,308.
Urea and amides have been disclosed as blocking agents in U.S. Pat. No. 5,817,732.
U.S. Pat. No. 4,302,351 discloses isocyanurates and acid hydrogen containing blocking agents.